The present application is closely related to a commonly assigned copending U.S. patent application Ser. No. 09/047,365 (corresponding to a Japanese Patent Application No. Hei-9-95095 entitled "Curved workpiece fabric holder device capable of enlarging embroidery stitching area for use in embroidery machine").
The present invention relates to a curved workpiece fabric holder device for holding cup-shaped or cylindrical workpiece fabric such as a cap in order to perform embroidery stitching onto the workpiece while rotating the same about its axis.
A multiple-head type embroidery machine is provided for performing embroidery stitching to a plurality of workpieces simultaneously. The multiple-head type embroidery machine includes a plurality of embroidery machines, a plurality of cylinder beds, a fabric feed frame movable in a Y-direction (frontward/rearward direction) in parallel with an extending direction of the cylinder beds and an X-direction (lateral direction) perpendicular to the Y-direction, and an embroidery frames detachably installed onto the fabric feed frame for fixing workpieces at embroidery stitching positions. Further, a curved workpiece fabric holder device is provided for each embroidery machine so as to hold a curved workpiece fabric in order to perform embroidery stitching to each curved workpiece fabric while retaining the curved workpiece fabric in the holder device. A cup-shaped or a cylindrical workpiece can be referred to as the curved workpiece fabric. For example, a cap is a typical example of the cup-shaped workpiece.
As described in a Japanese Patent Application Kokai No. Hei-8-232158, a conventional curved workpiece fabric holder includes a base frame positioned adjacent the cylinder bed and movable in the Y-direction, a rotary frame rotatable about an axis extending in the Y-direction, a workpiece retainer detachably mounted on the rotary frame for fixing the curved workpiece at an embroidery stitching position, and a translation mechanism for translating a liner movement of the fabric feed frame in the X-direction into the rotating motion of the rotary frame. The base frame is linked to the fabric feed frame through a link mechanism, so that the base frame and the rotary frame can be driven in the Y-direction concurrently with the movement of the fabric feed frame in the Y-direction.
The translation mechanism includes a pair of right and left link plates releasably fixed to the fabric feed frame, a connecting rod movably connected to the base frame for connecting together the right and left link plates, and a wire partly wound over the rotary frame and having each end fixed to each link plate. Even if the curved workpiece fabric holder is detached from the embroidery machine, the pair of link plates and the wire can provide a predetermined linking position with respect to the base frame.
If the pair of link plates are moved in the X-direction in accordance with the movement of the fabric feed frame, the rotary frame around which the wire is looped or wound is rotated about its axis, so that the curved workpiece and the retainer are also rotated. Thus, a desired stitching area can be brought into confrontation with a sewing needle.
In case where a plurality of curved workpiece fabrics are set onto the plurality of curved workpiece fabric holder devices and embroidery stitchings are to be simultaneously performed by the plurality of embroidery machines of the multiple-head type embroidery machine, each curved workpiece is provisionally set onto the retainer at a preparatory station, and then each retainer each retaining therein the curved workpiece is successively mounted onto each rotary frame. In this case, each rotary frame is set on a point of origin, and a setting position of the retainer to the rotary frame is fixed. Accordingly, a rotational position of the curved workpiece fabric with respect to the rotary frame is primarily determinative by the rotational position of the curved workpiece with respect to the retainer.
However, in the preparatory station, the curved workpiece is manually retained in the retainer. Therefore, a center of the curved workpiece fabric may be displaced from a center of the retainer as a result. In the latter case, embroidery stitching is performed at a position offset from an intended position of the curved workpiece. For example, in a baseball cap, an emblem is stitched at a front center of the cap. However, due to the erroneous retention of the cap in the retainer, the emblem is disadvantageously stitched at a displaced portion of the cap.
If identical embroidery stitchings are to be performed on the plurality of curved workpieces by the multiple head type embroidery machine, a plurality of curved workpiece fabric holder devices are driven by the single common fabric feed frame. If all curved workpiece fabrics are erroneously offset and offset angle are accidentally equal to one another, it is possible to simultaneously correct the offset position by moving the fabric feed frame. However, such phenomena is extremely rare. If one or several curved workpiece fabrics are set erroneously and even if the movement control of the workpiece fabric holder is contemplated for adjusting the erroneous position to a correct position, such adjustment then degrades or displaces the initial stitching position of the remaining previously correctly retained curved workpiece fabric. In other words, correction of the rotational position of the curved workpiece cannot be performed independently of each workpiece after these are set on the rotary frames. Therefore, if any incorrect rotational position is found by an operator, the operator must remove the retainer from the rotary frame, and must change the retaining position of the curved workpiece fabric relative to the retainer, and then, again install the retainer on the rotary frame. Consequently, it would be very difficult to enhance accuracy in embroidery stitching positions with respect to the. plurality of curved workpieces in case of the simultaneous embroidery stitching.
In another aspect of the conventional device, the wire looped around the rotary frame extends from a top end of the rotary frame toward each link plate fixed to a fabric feed frame, so that each end of the wire is fixed to each lower surface of the link plate by a fastener such as a screw.
In case a plurality of workpieces are to be stitched, a plurality of holder devices are mounted on the multiple head type embroidery machine. Here a distance between neighboring heads of the neighboring sewing machines is set in a predetermined distance, such as about 600 mm. In this connection, a pair of link plates for each holder device for fixing ends of each wire are set to the fabric feed frame in such a manner that the pair of link plates are not mechanically interfered with the neighboring link plates of different pairs. In each holder device, both fixed ends of the wire and the upper end of the rotary frame are aligned with each other in a horizontal direction. Because the rotary frame is not movable in the X-direction, the movement of the fabric feed frame in the X-direction causes rotation of the rotary frame through the translation mechanism.
Here, the embroidery stitching area is determinative by the rotation angle range of the rotary frame. That is, if the rotation angle range of the rotary frame is increased, the embroidery stitching area can be increased. In other words, the stitching area is determinative by the moving stroke of the fabric feed frame in the X-direction.
Further, the rotation angle range of the rotary frame is also dependent on a distance between the pair of link plates. If the pair of link plates are positioned far away from each other, a relatively long wire can be used so that rotation angle of the rotary frame can be increased. However, as described above, a distance between the pair of link plates is limited to avoid mechanical interference if a plurality of holder devices are installed onto the multiple head type embroidery machine. Therefore, it would be rather difficult to increase embroidery stitching area in the concurrent stitching in the multiple head type embroidery machine.